"Jimmy Kimmel Live" is the only program showing year-over-year gains in total viewers and in the 18- to 49-year-old demographic that advertisers covet most, according to Nielsen Media Research. Overall, the former "Man Show" host is up by 9 percent in total viewers and 4 percent in the younger demographic.

Both Colbert and Fallon lost viewers when compared to the same time last year in the key demographic. Colbert has gained in total viewers overall, however.

A key component in Kimmel's rise appears to be his 11:35 p.m. program's focus on big political topics and debate of the day, particularly on health care and gun control.

8. Jimmy Kimmel says he is willing to lose Republican viewers, but his ratings are going up

Jimmy Kimmel says he believes so strongly in his recent commentaries on health care and gun control that he is willing to lose Republican viewers who disagree with him.

So far, however, the late-night host's foray into divisive political issues has not hurt his ratings. If anything, it has helped.

On three consecutive nights in September, Kimmel used his opening monologue to rip a GOP health-care bill that did not guarantee insurance coverage for preexisting conditions. The following Monday, Kimmel scored a rare ratings win over rivals Stephen Colbert and Jimmy Fallon in the 18- to 49-year-old demographic coveted by advertisers.

As Variety's senior TV reporter, Daniel Holloway, wrote at the time, “buzz around the ABC host spiked in the past week.”

The first week of October, when Kimmel called for new gun-control measures after the mass shooting in Las Vegas, was his most-watched since June, when his show benefited from having the NBA Finals as a lead-in. Excluding that basketball-aided period, the first week of this month was Kimmel's best since January.